Fixed Rootfs in tests to handle symlink directories.
Fixed Rootfs in tests to handle symlink directories.

Review: https://reviews.apache.org/r/40002

asamerh4/mesos,jpeach/mesos,gsantovena/mesos,Gilbert88/mesos,abudnik/mesos,kaysoky/mesos,Gilbert88/mesos,andschwa/mesos,zmalik/mesos,chhsia0/mesos,verizonlabs/mesos,verizonlabs/mesos,asamerh4/mesos,kaysoky/mesos,craimbert/mesos,dforsyth/mesos,kaysoky/mesos,dforsyth/mesos,neilconway/mesos,gsantovena/mesos,kaysoky/mesos,chhsia0/mesos,jpeach/mesos,neilconway/mesos,Aman-Jain-14/customizedMesos,reneploetz/mesos,andschwa/mesos,jpeach/mesos,Gilbert88/mesos,yuquanshan/customizedMesos,zmalik/mesos,andschwa/mesos,neilconway/mesos,Gilbert88/mesos,chhsia0/mesos,chhsia0/mesos,dforsyth/mesos,reneploetz/mesos,Gilbert88/mesos,kaysoky/mesos,asamerh4/mesos,reneploetz/mesos,dforsyth/mesos,yuquanshan/customizedMesos,neilconway/mesos,zmalik/mesos,yuquanshan/customizedMesos,abudnik/mesos,yuquanshan/customizedMesos,craimbert/mesos,yuquanshan/customizedMesos,andschwa/mesos,andschwa/mesos,chhsia0/mesos,reneploetz/mesos,jpeach/mesos,craimbert/mesos,abudnik/mesos,andschwa/mesos,reneploetz/mesos,reneploetz/mesos,zmalik/mesos,Gilbert88/mesos,craimbert/mesos,Aman-Jain-14/customizedMesos,andschwa/mesos,jpeach/mesos,gsantovena/mesos,reneploetz/mesos,neilconway/mesos,verizonlabs/mesos,zmalik/mesos,dforsyth/mesos,Aman-Jain-14/customizedMesos,asamerh4/mesos,jpeach/mesos,kaysoky/mesos,abudnik/mesos,Gilbert88/mesos,zmalik/mesos,dforsyth/mesos,asamerh4/mesos,craimbert/mesos,yuquanshan/customizedMesos,asamerh4/mesos,yuquanshan/customizedMesos,craimbert/mesos,Aman-Jain-14/customizedMesos,chhsia0/mesos,kaysoky/mesos,abudnik/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,verizonlabs/mesos,zmalik/mesos,gsantovena/mesos,chhsia0/mesos,verizonlabs/mesos,asamerh4/mesos,neilconway/mesos,neilconway/mesos,dforsyth/mesos,craimbert/mesos,abudnik/mesos,gsantovena/mesos,jpeach/mesos,abudnik/mesos,Aman-Jain-14/customizedMesos,gsantovena/mesos,verizonlabs/mesos,verizonlabs/mesos,Aman-Jain-14/customizedMesos